What is atherosclerosis?

Atherosclerosis refers to the build up of fatty deposits called plaques in the walls of the arteries.

Over time these deposits of cholesterol, fat and the smooth muscle cells that line the arteries are transformed into a thickened and sometimes calcified mass (atheroma).

Atheroma causes the arteries to narrow and lose their elasticity, which leads to a reduction in blood flow through the vessels.

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What is an artery?

An artery is a blood vessel.

The main function of the artery is to carry blood from the heart to the tissues and organs of the body, as opposed to veins, which carry blood from tissues and organs back to the heart.

When a blockage in an artery occurs, the tissue supplied by that artery is denied the nutrients found in blood, some of which are essential for life, such as oxygen.

The coronary arteries carry blood to the heart muscle.

What are the symptoms of atherosclerosis?

The hardening and narrowing process of atherosclerosis takes many years, indeed decades, and initially causes no symptoms, but when fatty deposits build up to an extent that the artery is significantly damaged, it can result in any of the following.

Blood clots (thrombus)

A blood clot can form on the cholesterol plaque leading to a blockage in the artery, so preventing blood flow down the artery and depriving tissues of vital nutrients.

The fatty deposits of atheroma in the arteries are sited within the wall of the artery and are completely covered by a lining of protective cells from the flowing blood.

If this protective cell barrier breaks down – in other words if the plaque ruptures – then blood is exposed to a very high concentration of cholesterol in the artery wall.

This leads to activation of the blood clotting system around the rupture, and the development of a blood clot that may be large enough to block the artery and seal off the blood supply to whatever organ is supplied by that artery.

Depending on where the block is, it may cause stroke, angina (chest pains because the heart lacks oxygen) or a heart attack.

When rupture of the atherosclerotic plaque occurs, blood clots can form very quickly, within minutes of the rupture.

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Ischaemic stroke

A blood clot can cut off the supply of oxygen to an area of the brain.

Depending on the size of the affected area and amount of damaged brain tissue, this can cause paralysis, typically affecting only one side of the body.

Most strokes are ischaemic; there is evidence that treatment of stroke with clot busting drugs improves the chances for recovery, provided such treatment is given very early (within 3 hours) of the onset.

Haemorrhagic stroke

Arteries that are diseased by the atherosclerotic process are not only prone to developing blood clots within them, they are also weaker than normal, and can burst open due to the pressure of the arterial blood flow.

When a brain artery affected by atherosclerosis ruptures, usually in someone who also has high blood pressure, considerable brain damage can occur. This can cause a particularly severe form of stroke.

Diabetes: this is true for all causes of diabetes, though in the childhood form (called type I) atherosclerosis may take decades to appear, whereas in the more common adult (type II, weight related) form, atherosclerosis can appear within a few years.

Being male. Women experience similar levels of atherosclerosis, but are affected about 5 to 10 years later than men.

Race, South Asians, and some other races, are at increased risk of developing atherosclerosis.

There's some evidence that high levels of psychological stress also increase risk.

What can be done to prevent atherosclerosis?

Stop smoking. Your doctor or pharmacist will be able to provide advice about stop-smoking programmes and medicines that can help you quit. Even if you don't smoke yourself, try and reduce your exposure to other people smoking (second-hand smoke).

Regular physical exercise: aim for a half-hour exercise session each day, but even several shorter bouts will do. While brisk walking is helpful, aim to exercise more vigorously to improve your fitness – try use a bicycle ergometer, swimming, running on a treadmill or using a cross-trainer. Aim to exercise sufficiently intensely to make yourself noticeably breathless, and maintain this level for at least 20 minutes. Repeat at least 3 times a week, preferably more. In essence, the greatest benefits are seen in people who change sedentary habits into lifestyle with at least regular moderate activity.

Eat a varied and healthy diet with plenty of leafy vegetables. Avoid sugary foods and saturated fats found in red meat and full-fat dairy products. Add fish to your diet once or twice a week.

Lose weight if you are overweight. This can be done by adjusting your diet in combination with regular physical activity. In this case physical activity is the more important than a weight reducing diet for diminishing the risk of atherosclerosis.

In patients at high risk of atherosclerosis, drugs to lower blood pressure (even if the blood pressure is in the normal range), or cholesterol (of which the commonest drugs used are from the statin class) may be used.

This is very important in those people at very high risk of blood clots – doctors can estimate your risk from a risk prediction chart, of which there are various forms around – you should always ask your doctor what your risk is, this is usually presented as a 10-year risk of heart attack and stroke.

If atherosclerosis in the coronary arteries builds up to such an extent that it interferes with the blood supply to the heart muscle, it can be treated with medication.

These medicines reduce the heart's need for oxygen, thereby lowering pressure on the heart and improving pumping ability.

Severe narrowing and blockage can also be treated by the following surgical techniques.

Balloon dilation (called percutaneous coronary intervention or PCI): the narrowed coronary artery is dilated (opened up) with a balloon. A good long-term result can be achieved by then inserting a metal stent (tube) to keep the artery open. Stents sometimes are coated with a drug to reduce the chance of the narrowing coming back.

Bypass operation: a section of blood vessel is taken from another part of your body and joined to the blocked artery to bypass the obstruction to blood flow. The blood vessel used for the bypass is either a vein from the leg, or a spare artery that runs just under the breast-bone, the internal mammary artery. Occasionally an artery from the arm is used (the radial artery).

Cleaning the artery (endarterectomy): surgery is used to scrape the fatty plaques from inside the arteries. This operation is only used for repairing the carotid arteries in the neck.

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